Wireless communications circuitry with temperature compensation

ABSTRACT

A test system for calibrating wireless electronic devices is provided. The test system may include a test host, a radio communication tester, and a temperature chamber in which an electronic device under test (DUT) may be tested. The DUT may include a temperature sensor for monitoring an internal temperature of the DUT and may include power amplifier circuitry for outputting radio-frequency test signals. The tester may be used to measure output power levels of the radio-frequency test signals when the DUT is operating at a given reference temperature and when the DUT is operating at target operating temperature levels other than the given reference temperature. Power amplifier output level offset compensation values may be computed by comparing output power levels measured at each of the target operating temperatures to output power levels measured at the given reference temperature and may be stored in the DUT prior to normal operation.

BACKGROUND

Electronic devices often contain wireless communications capabilities.For example, portable electronic devices are often provided withwireless local area network (WLAN) communications circuitry, cellulartelephone communications circuitry, and satellite navigation systemreceiver circuitry such as Global Positioning System (GPS) receivercircuitry. Using wireless communications circuits such as these, a usermay communicate with local and remote wireless networks and may receivesignals from GPS satellites.

As an example, a cellular telephone may include cellular telephonetransceiver circuitry that is used to make telephone calls. The cellulartelephone transceiver circuitry includes power amplifier circuitry thatis used to amplify radio-frequency (RF) signals so that the RF signalscan be transmitted to a nearby base station. If care is not taken, achange in temperature resulting from operation of the power amplifiercircuitry can adversely affect the cellular telephone's ability totransmit RF signals at desired output power levels.

Consider a scenario in which a cellular telephone transmits RF signalsto a current serving base station when the cellular telephone has aninternal temperature of 40° C. The transmitted signals may be receivedby the current serving base station at a satisfactory power level of −10dBm. As the power amplifier circuitry transmits the RF signals to thebase station and generates heat in the process, the internal temperatureof the cellular telephone may increase over time. When the internaltemperature of the cellular telephone reaches 55° C., theradio-frequency signals that are transmitted by the cellular telephonemay be received by the current serving base station at an unacceptablylow power level of −15 dBm. As shown in this example, a change in theinternal temperature of the cellular telephone can degrade the wirelessoutput capability of the cellular telephone.

It would therefore be desirable to be able to provide ways for operatinga wireless electronic device while taking into account variations in theoperating temperature.

SUMMARY

Electronic devices may include wireless communications circuitry forsupporting wireless operation and may also include temperature sensingcircuits configured to monitor device operating temperatures. Thewireless communications circuitry within an electronic device may, forexample, include transceiver circuitry, power amplifier circuitry, andantenna structures.

The transceiver circuitry may be used to generate radio-frequencysignals. The power amplifier circuitry may be used to amplify theradio-frequency signals so that the radio-frequency signals may beradiated from the antenna structures at sufficiently high output powerlevels. The performance of the power amplifier circuitry may vary as thedevice operating temperature changes.

Such types of electronic devices may be calibrated using a test systemto obtain power amplifier offset compensation values that compensate forthe change in power amplifier performance across different deviceoperating temperatures. In one suitable embodiment, the test system mayinclude a test host (e.g., a personal computer), a radio-frequencycommunications tester (e.g., a universal radio communication tester), apower supply unit, and a test chamber (e.g., a temperature chamber).

During calibration, an electronic device under test (DUT) may be placedwithin the test chamber. The test host may configure the internaltemperature of the test chamber to a selected reference temperature. Thetest host may then configure the DUT to transmit radio-frequency testsignals to the radio communication tester (e.g., using differentradio-frequency power amplifier gain settings at desired frequencies).The radio communication tester may receive the corresponding testsignals and perform desired output power measurements. The output powermeasurements gathered while the test chamber is set to the referencetemperature may serve as baseline output power measurements to whichother output power measurements are compared during computation of thepower amplifier offset compensation values. The test host may alsoobtain a temperature sensor output value from the DUT using thetemperature sensing circuit. The sensor output value corresponding tothe reference temperature may represent a baseline reference sensoroutput value from which other target device operating temperatures(sometimes referred to as target calibration temperature levels) may becomputed.

The test host may compute target sensor output values corresponding toeach target device operating temperature in a predetermined list oftarget device operating temperatures using the baseline reference sensoroutput value and a known temperature coefficient associated with thetemperature sensing circuit. The test host may then adjust thetemperature chamber so that the DUT is tested at each of the targetdevice operating temperatures (e.g., the radio communication tester maybe used to obtain output power measurements while the sensor outputvalues are sufficiently close to the computed target sensor outputvalues).

Output power measurements measured in this way may be compared to thebaseline output power measurements to determine output power offsetvalues as a function of device operating temperature. Offset valuesobtained in this way can be stored in the device as calibration data.During normal operation, the electronic device may adjust the wirelesscommunications circuitry using the calibration data so radio-frequencyperformance is optimized across different device operating temperatures(as detected by the temperature sensing circuit).

Further features of the present invention, its nature and variousadvantages will be more apparent from the accompanying drawings and thefollowing detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of an illustrative electronic device with wirelesscommunications circuitry and a temperature sensor in accordance with anembodiment of the present invention.

FIG. 2 is a plot of radio-frequency output power level versusradio-frequency gain index associated with the wireless communicationscircuitry in the electronic device of FIG. 1 in accordance with anembodiment of the present invention.

FIG. 3 is a diagram of an illustrative test system that in includes atemperature chamber in which the electronic device of FIG. 1 can becalibrated in accordance with an embodiment of the present invention.

FIG. 4 is a plot of a temperature dependent sensor output valuegenerated by the temperature sensor in the electronic device of FIG. 1versus device operating temperature in accordance with an embodiment ofthe present invention.

FIG. 5 is a flow chart of illustrative steps for computing targettemperature sensor output values corresponding to respective targetdevice operating temperatures in accordance with an embodiment of thepresent invention.

FIG. 6 is a table showing illustrative test data gathered using at leastsome of the steps of FIG. 5 in accordance with an embodiment of thepresent invention.

FIG. 7 is a table of computed target temperature sensor output values inaccordance with an embodiment of the present invention.

FIG. 8 is a flow chart of illustrative steps for using the test systemof the type shown in FIG. 3 to measure radio-frequency output powerlevels at each target device operating temperature in accordance with anembodiment of the present invention.

FIG. 9 is a table showing illustrative test data gathered using at leastsome of the steps of FIG. 8 in accordance with an embodiment of thepresent invention.

FIG. 10 is a flow chart of illustrative steps for computing temperaturedependent output power offset compensation values in accordance with anembodiment of the present invention.

FIG. 11A is a plot showing how radio-frequency output power levelsmeasured using the steps of FIG. 8 may vary as a function of deviceoperating temperature in accordance with an embodiment of the presentinvention.

FIG. 11B is a plot showing temperature dependent power supply levelsthat may be supplied to the wireless communications circuitry in theelectronic device of FIG. 1 for compensating radio-frequency outputpower offsets in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION

This relates generally to electronic devices, and more particularly, toelectronic devices having wireless communications capabilities.

Electronic devices that include wireless communications circuitry may beportable electronic devices such as laptop computers or small portablecomputers of the type that are sometimes referred to as ultraportables.Portable electronic devices may also be somewhat smaller devices. Thewireless electronic devices may be, for example, cellular telephones,media players with wireless communications capabilities, handheldcomputers (also sometimes called personal digital assistants), remotecontrollers, global positioning system (GPS) devices, tablet computers,and handheld gaming devices. Wireless electronic devices such as thesemay perform multiple functions. For example, a cellular telephone mayinclude media player functionality and may have the ability to rungames, email applications, web browsing applications, and othersoftware.

FIG. 1 shows an illustrative electronic device that includes wirelesscommunications circuitry such as wireless communications circuitry 12.As shown in FIG. 1, wireless communications circuitry 12 may include atleast baseband processor 18, wireless transceiver circuitry 14,radio-frequency (RF) front end circuitry 19, and one or more antennas(antenna structures) 34. Front end circuitry 19 may include poweramplifier circuitry 20, filter circuitry 28, impedance matchingcircuitry 32, and other suitable radio-frequency circuits. During signaltransmission operations, transceiver circuitry 14 may supplyradio-frequency signals that are transmitted by antennas 34. Duringsignal reception operations, circuitry 14 may accept radio-frequencysignals that have been received by antennas 34.

The antenna structures and transceiver circuits of device 10 may be usedto support communications over any suitable wireless communicationsbands. For example, wireless communications circuitry 12 may be used tocover communications frequency bands such as cellular telephone voiceand data bands at 700 MHz, 850 MHz, 900 MHz, 1800 MHz, 1900 MHz, and thecommunications band at 2100 MHz band, the Wi-Fi® (IEEE 802.11) bands at2.4 GHz and 5.0 GHz (also sometimes referred to as wireless local areanetwork or WLAN bands), the Bluetooth® band at 2.4 GHz, the GlobalPositioning System (GPS) band at 1575 MHz, and Global NavigationSatellite System (GLONASS) band at 1602 MHz.

Device 10 may be used to cover these communications bands and othersuitable communications bands with proper configuration of the antennastructures in wireless communications circuitry 12. Any suitable antennastructures may be used in device 10. For example, device 10 may have oneantenna or may have multiple antennas. The antennas in device 10 mayeach be used to cover a single communications band or each antenna maycover multiple communications bands. If desired, one or more antennasmay cover a single band while one or more additional antennas are eachused to cover multiple bands.

Device 10 may include storage and processing circuitry such as storageand processing circuitry 16. Storage and processing circuitry 16 mayinclude one or more different types of storage such as hard disk drivestorage, nonvolatile memory (e.g., flash memory or otherelectrically-programmable-read-only memory), volatile memory (e.g.,static or dynamic random-access-memory), etc. Storage and processingcircuitry 16 may be used in controlling the operation of device 10.Processing circuitry in circuitry 16 may be based on processors such asmicroprocessors, microcontrollers, digital signal processors, dedicatedprocessing circuits, power management circuits, audio and video chips,radio-frequency transceiver processing circuits, radio-frequencyintegrated circuits of the type that are sometimes referred to asbaseband modules, and other suitable integrated circuits.

Storage and processing circuitry 16 may be used in implementing suitablecommunications protocols. Communications protocols that may beimplemented using storage and processing circuitry 16 include internetprotocols, wireless local area network protocols (e.g., IEEE 802.11protocols—sometimes referred to as Wi-Fi®), protocols for othershort-range wireless communications links such as the Bluetooth®protocol, protocols for handling 2G cellular telephone communicationsprotocols such as GSM (Global System for Mobile Communications) and CDMA(Code Division Multiple Access), 3G cellular telephone communicationsprotocols such as UMTS (Universal Mobile Telecommunications System) andEV-DO (Evolution-Data Optimized), 4G cellular telephone communicationsprotocols such as LTE, etc.

Data signals that are to be transmitted by device 10 may be provided tobaseband processor 18 (sometimes referred to as a baseband module).Baseband processor 18 may be implemented using a single integratedcircuit (e.g., a baseband processor integrated circuit) or usingmultiple integrated circuits.

Baseband processor 18 may receive signals to be transmitted via antennas34 over path 13 from storage and processing circuitry 16. Basebandprocessor 18 may provide signals that are to be transmitted totransmitter circuits within transceiver circuitry 14. The transmittercircuits may be coupled to radio-frequency power amplifier circuitry 20via a transmit (TX) path such as path 26. Path 13 may also carry controlsignals from storage and processing circuitry 16. These control signalsmay be used to control the power of the radio-frequency signals that thetransmitter circuits within transceiver circuitry 14 supplies to theinput of power amplifiers 20 via path 26. For example, the controlsignals may be provided to a variable gain amplifier located insidetransceiver circuitry 14 that controls the power of the radio-frequencysignals supplied to the input of power amplifiers 20. This transmittedradio-frequency signal power level is sometimes referred to herein asPin, because it represents the input power to power amplifier circuitry20.

During data transmission, power amplifier circuitry 20 may boost theoutput power of transmitted signals to a sufficiently high level toensure adequate signal transmission. Filter circuitry 28 may contain aradio-frequency duplexer and other radio-frequency output stagecircuitry such as radio-frequency switches and passive elements.Switches may, if desired, be used to switch the wireless circuitrybetween a transmitting mode and a receiving mode. Duplex filter 28(sometimes referred to as a duplexer) may be used to route input andoutput signals based on their frequency.

Matching circuitry 32 may include a network of passive components suchas resistors, inductors, and capacitors and may be used to ensure thatantenna structures 34 are impedance matched to the rest of the wirelesscommunications circuitry. Wireless signals that are received by antennastructures 34 may be passed to receiver circuitry in transceivercircuitry 14 over a receive (RX) path such as path 36.

Each radio-frequency power amplifier (e.g., each power amplifier inpower amplifier circuitry 20) may include one or more power amplifierstages such as stages 22. As an example, each power amplifier may beused to handle a separate communications band and each such poweramplifier may have three series-connected power amplifier stages 22.Stages 22 may have power supply terminals such as terminals 24 thatreceive bias voltages. Bias supply voltage may be supplied to terminals24 using path 42. Control signals from storage and processing circuitry16 may be used to selectively enable and disable stages 22 or to controlthe gain of individual stages using control path 44.

By enabling and disabling stages 22 selectively and/or adjusting thegain of individual stages separately, the power amplifier may be placedinto different power modes. For example, the power amplifier may beplaced into a high power mode (sometimes referred to as high gain mode)by enabling all three of power amplifier stages 22 or may be placed intoa low power mode (sometimes referred to as low gain mode) by enablingtwo of the power amplifier stages. Other configurations may be used ifdesired.

For example, a very low power mode may be supported by turning on onlyone of three gain stages or arrangements with more than three power modesettings may be provided by selectively enabling other combinations ofgain stages (e.g., in power amplifiers with three or more than threegain stages). In one suitable embodiment of the present invention, thegain of power amplifier circuitry 20 may be fine-tuned by adjusting aradio-frequency gain index (RGI). Incrementing the gain index may, forexample, increase the amount of bias current that is provided to one ormore of the stages to increase the gain and/or maximum power output ofthe power amplifier (e.g., control signals may be provided via path 44that adjust the amount of bias currents provided to amplifiers 22 overpath 42).

FIG. 2 is a plot showing output power level Pout for signals generatedat the output of power amplifier circuitry 20 as a function of RGI. Asshown in FIG. 2, characteristic curve 200 may represent output powerlevels for amplifier 20 operating in high gain mode, whereascharacteristic curve 202 may represent output power levels for amplifier20 operating in low gain mode. In this example, Pout may bemonotonically increased from 5 dBm to 25 dBm as gain index is swept from0 to 31 when amplifier circuit 20 is configured in low gain mode. Whenamplifier circuitry 20 is configured in high gain mode, Pout may bemonotonically increased from 10 dBm to 35 dBm as gain index is raisedfrom 0 to 31. The values as shown in FIG. 2 are merely illustrative. Byadjusting the power mode and gain index of the amplifier, the outputpower capabilities of power amplifier circuitry 20 may be adjusted tomaximize efficiency (e.g., for any given output power).

Device 10 may include adjustable power supply circuitry such as powersupply circuitry 38. Adjustable power supply circuitry 38 may becontrolled by control signals received over control path 40. The controlsignals may be provided to adjustable power supply circuitry 38 fromstorage and processing circuitry 16 or any other suitable controlcircuitry (e.g., circuitry implemented in baseband module 18, circuitryin transceiver circuitry 14, etc.).

The performance of wireless communications circuitry 12 may be affectedby variations in device operating conditions. Consider a scenario inwhich device 10 includes a cellular telephone transceiver 14 that isbeing used to make a voice call (e.g., transceiver 14 is configured totransmit radio-frequency signals to a nearby cell tower). At thebeginning of the voice call, the transmitted signals arriving at thenearby cell tower may exhibit satisfactory signal levels. Over time,however, power amplifier circuitry 20 that is being used to amplify theradio-frequency signals generates heat that can cause the internaltemperature of device 10 (sometimes referred to as device operatingtemperature) to rise. As the device operating temperature rises, theefficiency of wireless communications circuitry 12 may be degraded, andsignals transmitted from device 10 may no longer be received by thenearby cell tower at satisfactory signal levels (i.e., power amplifiercircuitry 20 may experience an output power offset). It may therefore bedesirable to have a way of monitoring the internal temperature of DUT 10and to calibrate the performance of circuitry 12 across differentoperating temperatures (e.g., to obtain power amplifier output poweroffset compensation values that take into account variations in deviceoperating conditions).

Device 10 may include a temperature sensing circuit such as temperaturesensor 100. The example of FIG. 1 in which temperature sensor 100 isshown to be part of wireless communications circuitry 12 is merelyillustrative. Temperature sensor 100 may, as an example, include athermistor configured to output Dtemp and a reference clock temperaturesensor configured to output temp. For example, temperature sensor 100may produce a temperature dependent output value Dtemp that isproportional to the device operating temperature and may produce atemperature dependent output value Ctemp that is proportional to thetemperature of a reference clock on the device. In one suitableembodiment of the present invention, sensor output value Dtemp may beoutput in the form of a digital signal. In other suitable embodiments,sensor output value Dtemp may be output in the form of an analog signal.Sensor outputs Dtemp and Ctemp may be fed to storage and processingcircuitry 16 via path 102.

Storage and processing circuitry 16 may maintain a table ofpredetermined control settings or other stored information to be used incontrolling power supply circuitry 38. The table may include a list ofbias voltages (Vcc values) that are to be supplied by adjustable powersupply circuitry 38 (as an example). Based on the known operatingconditions of circuitry 20 such as its current gain settings (e.g., ahigh power mode or a low power mode), the desired output power valuePout to be produced by power amplifier circuitry 20 (e.g., the outputpower from amplifier circuitry 20 as measured at its output), thedesired transmit frequency, the current device operating temperature asmeasured using temperature sensing circuit 100, and based on the valuesof the predetermined control settings in the table, storage andprocessing circuitry 16 may generate appropriate control signals on path40 (e.g., analog control voltages or digital control signals).

The control signals that are supplied by storage and processingcircuitry 16 on path 40 may be used to adjust the magnitude of thepositive power supply voltage Vcc (sometimes referred to as theamplifier bias) that is provided to power amplifier circuitry 20 overpath 42 (as an example). In other suitable arrangements, storage andprocessing circuitry 16 may generate appropriate control signals on path44 that configure power amplifier circuitry 20 in the desired state.These adjustments may be made during testing and during normal operationof device 10 to help compensate for changes in the performance ofwireless communications circuitry 12 across different device operatingconditions (e.g., across different operating temperatures as measured bysensor 100, across different amplifier gain modes/settings, acrossdifferent operating frequencies, across different radio accessprotocols, etc.).

FIG. 3 is a diagram of an illustrative test system 110 that can be usedto calibrate device 10. Device 10 being tested/calibrated may sometimesbe referred to as a device under test (DUT). Test system 110 may includea test host such as test host 112 (e.g., a personal computer), a radiocommunication tester such as radio communication tester 114, a powersupply unit such as power supply unit 116, a test chamber such astemperature chamber 118, control circuitry, network circuitry, cabling,and other test equipment.

DUT 10 may be placed within test chamber 118 during testing. Testchamber 118 may include a temperature control unit 120 that is used toregulate the temperature within test chamber 118. Temperature controlunit 120 may be adjusted using control signals provided from test host112 over path 122. For example, test host 112 may send first controlsettings to unit 120 that direct control unit 120 to heat up theinternal temperature of chamber 118 to 73° C. As another example, testhost 112 may send second control settings to unit 120 that direct unit120 to cool down the internal temperature of chamber 118 to −9° C. Testchamber 118 may therefore sometimes be referred to as a test oven thatprovides a controlled user-specified oven temperature. In general,temperature control unit 120 may be configured to precisely set thetemperature within test chamber 118 to any desired level.

As shown in FIG. 3, DUT 10 may be coupled to test host 112 via conductedpath 124. The connection represented by path 124 may be a UniversalSerial Bus (USB) based connection, a Universal AsynchronousReceiver/Transmitter (UART) based connection, or other suitable types ofconnections. Test host 112 may send control signals to DUT 10 over path124 for directing the operation of DUT 10 during testing. For example,test host 112 may send commands to DUT 10 that configure power amplifier20 in a selected gain mode, that configure transceiver circuitry 14 togenerate radio-frequency signals using desired modulation schemes atdesired frequencies, etc.

Power supply unit 116 may serve to supply power to DUT 10 during testingvia path 130. In particular, power supply unit 116 can be used tomonitor current Isupp that is drawn by DUT 10 during testing. Datareflective of the amount of current Isupp drawn by DUT 10 over time maybe provided from power supply unit 116 to test host 112 via path 131.Monitoring current Isupp in this way ensures that DUT 10 does notconsume excessive amounts of power when power amplifier circuitry 20 isoperated under high gain settings. Current Isupp data gathered usingthis approach may also be useful when computing power amplifier outputefficiency.

Radio communication tester 114 may, for example, be a radiocommunication tester (e.g., the MT8820 Universal Radio CommunicationAnalyzer available from Anritsu) that is used to perform radio-frequencyparametric tests for a variety of different radio-frequencycommunications bands and channels. DUT 10 may include a conductivemember 128 interposed in a transmission line path connecting poweramplifier circuitry 20 and antenna structures 34. Tester 114 may becoupled to conductive member 128 via a radio-frequency test cable 126(e.g., a coaxial cable). Test cable 126 may make contact with member 128of DUT 10 via mating radio-frequency connectors, via a test probe, orvia other suitable coupling mechanisms.

Arranged in this way, antenna structures 34 may be decoupled from theremainder of the wireless communications circuitry while cable 126 iscoupled to member 128, and tester 114 may be used to receiveradio-frequency test signals generated at the output of power amplifiercircuitry 20. Tester 114 may be used to analyze the RF test signalsreceived from DUT 10. Test host 112 may retrieve the analyzed resultsvia path 113. Test host 112 may then compute calibration values (e.g.,temperature dependent power amplifier output offset compensation values)using the retrieved test data.

Test system 110 as shown in FIG. 3 is merely illustrative and does notserve to limit the scope of the present invention. If desired, testsystem 110 may include other means of controlling and monitoring theoperating conditions of DUT 10, may include other types ofradio-frequency test units for measuring the performance of DUT 10, andmay include any other suitable test equipment.

FIG. 4 shows a plot of temperature sensor output value Dtemp as afunction of temperature. As shown by line 210 in FIG. 4, Dtemp maydecrease as temperature is increased. For example, a temperature of −30°C. may result in temperature sensor 100 generating a Dtemp of 2788; atemperature of 25° C. may result in temperature sensor 100 generating aDtemp of 2540; and a temperature of 85° C. may result in temperaturesensor 100 generating a Dtemp of 2270. In this example, temperaturesensor 100 exhibits a temperature coefficient k of −4.5 (i.e., the slopeof line 210 is equal to −4.5). The temperature coefficient k oftemperature sensor 100 is generally a known, fixed value. By monitoringoutput value Dtemp, an accurate reading of the internal temperature ofDUT 10 relative to a baseline temperature reading can therefore beobtained.

In the example of FIG. 4, consider a scenario in which sensor 100outputs a Dtemp of 2405. If it is known that at a reference temperatureof 25° C. corresponds to a baseline Dtemp equal to 2540, it can bedetermined that the current internal operating temperature of DUT 10 isequal to 55° C. ([2405−2540]/[−4.5]+25). Consider another scenario inwhich sensor 100 outputs a Dtemp of 2720. Using the known temperaturecoefficient of sensor 100 and the baseline temperature reading at 25°C., it can similarly be determined that the current internal operatingtemperature of DUT 10 is equal to −15° C. (([2720−2540]/[−4.5]+25). Inother words, once a baseline temperature sensor reading is made at areference temperature, the internal operating temperature of DUT 10 canbe precisely computed using the baseline temperature output and theknown temperature coefficient (e.g., the computed temperature valueswill be accurate relative to the reference temperature).

In computing output power offset compensation values for power amplifiercircuitry 20, it may first be desirable to obtain baseline measurementsat a selected reference temperature. FIG. 5 shows illustrative steps forobtaining baseline output power measurements at a reference temperatureof 25° C. using test system 110 of the type described in connection withFIG. 3.

At step 300, DUT 10 may be placed within temperature chamber 118. Atstep 302, test host 112 may control temperature control unit 120 to setthe internal temperature of chamber 118 to the reference temperature of25° C. At step 304, DUT 10 may repeatedly record Dtemp and Ctempmeasured using temperature sensor 100 while wireless communicationscircuitry 12 is turned off (e.g., n Dtemp measurements may be stored incircuitry 102 while transceiver circuitry 14 and power amplifiercircuitry 20 are in an off state). Ctemp measurements may be used tocompute an offset between the internal temperature of DUT 10 and theoven temperature.

At step 306, wireless communications circuitry 12 may be turned on(e.g., transceiver circuitry 14 and power amplifier circuitry 20 may beplaced in an active transmission state). At step 308, test host 112 mayconfigure DUT 10 so that power amplifier circuitry 20 is set to operatein the low gain mode (see, FIG. 2).

At step 310, a radio communication tester 114 may be used to measure theoutput power level of power amplifier circuitry 20 while sweeping theradio-frequency gain index from RGI_(MIN) to RGI_(MAX) (e.g., from 0 to31). In particular, transceiver 14 may be configured to outputradio-frequency test signals using desired modulation schemes (i.e., atdifferent data rates) at desired frequencies (i.e., in differentfrequency bands and channels). If desired, DUT 10 may again record Dtempto ensure that the internal temperature of DUT 10 has not changed by anunacceptable amount since step 304 (e.g., m Dtemp measurements may bestored in circuitry 102 after the output power levels have been measuredusing tester 114).

At step 312, test host 112 may configure DUT 10 so that power amplifiercircuitry 20 is set to operate in the high gain mode, and tester 114 maybe used to measure the output power level of power amplifier circuitry20 while gain index is swept from RGI_(MIN) to RBI_(MAX) (e.g., theoperations of step 310 may be repeated for characterizing the outputefficiency of circuitry 20 in high gain mode). If desired, DUT 10 mayagain record Dtemp to ensure that the internal temperature of DUT 10 hasnot changed by an unacceptable amount since step 310.

At step 314, wireless communications circuitry 12 may be turned off(e.g., transceiver circuitry 14 and power amplifier circuitry 20 may beplaced in the idle mode). At step 316, test host 112 may be used tocompute a target baseline Dtemp for DUT 10 operating under an oventemperature of 25° C. by averaging measured Dtemp values gathered duringsteps 304, 310, and 312. At step 318, target Dtemp values for othertarget device operating temperature levels may be computed using onlythe computed baseline Dtemp and the known temperature coefficient k oftemperature sensor 100.

FIG. 6 shows a table of illustrative transmit power measurements thatcan be gathered during step 310 of FIG. 5. As shown in FIG. 6, TX powerlevels can be recorded for signals transmitted in radio-frequencychannel C1 in band B1 while sweeping RGI from 0 to 31, where thetransmitted signals are modulated using 8 Phase Shift Keying (8PSK) andGaussian Minimum Shift Keying (GMSK) digital modulation schemes, andwhere power amplifier circuitry 20 is configured in low gain mode (i.e.,circuitry 20 has a gain mode value of zero). Values Dtemp1 may representan average value computed using the n Dtemp measurements obtained atstep 304. Values Dtemp2 may represent an average value computed usingthe m Dtemp measurements obtained at step 312. The transmit power levelsmeasured at the reference oven temperature of 25° C. may representbaseline transmit power levels from which offset compensation values canbe computed.

The values shown in FIG. 6 are merely illustrative. In general, testsystem 110 may be configured to obtain TX power level measurements forany number of radio-frequency channels in any number of radio-frequencybands, for radio-frequency signals transmitted using any desiredfrequency modulation schemes (e.g., for radio-frequency signalsmodulated using Binary Phase Shift Keying (BPSK), Quadrature Phase ShiftKeying (QPSK), 16 Quadrature Amplitude Modulation (16-QAM), 64-QAM,etc.), and for any number of power amplifier gain settings (e.g., whenpower amplifier circuitry 20 is configured in a low gain mode, in a highgain mode, or in any intermediate gain modes and when power amplifiercircuitry 20 is adjusted across different radio-frequency gain indexsettings).

FIG. 7 is a table that includes target operating temperatures levels andcorresponding target sensor output values Dtemp that can be computedduring steps 316 and 318 of FIG. 5. At step 316, the target Dtempcorresponding to an operating temperature of 25° C. (i.e., the referencetemperature) may be computed by averaging at least Dtemp1 and Dtemp2(see, FIG. 6). The resulting target Dtemp value of 2370 ([2373+2367]/2)as shown in FIG. 7 may represent the baseline Dtemp from which all othertarget Dtemp values are computed.

The values listed in column 350 may represent a predetermined list oftarget operating temperatures under which DUT 10 should be calibrated.These values may therefore sometimes be referred to as targetcalibration temperature levels. The list of target temperature values inFIG. 7 ranges from −30° C. to 85° C. and is meant to cover a wide rangeof operating conditions for device 10. The values listed in column 352represent incremental changes in temperature from one target operatingtemperature to the next. The values listed in column 354 may be computedby multiplying the ΔTEMP values of column 352 by the known temperaturecoefficient k of temperature sensor 100. In this example, thetemperature coefficient k of sensor 100 is equal to −4.0. For instance,the change in Dtemp (ΔDtemp) corresponding to the target temperature of39° C. may be equal to −56 (14*−4), whereas ΔDtemp corresponding to thetarget temperature of −15 may be equal to 64 (−16*−4).

At step 318 of FIG. 5, the target Dtemp values may be calculated byadding the computed ΔDtemp values to the baseline Dtemp value of 2370.For example, the target Dtemp corresponding to the target operatingtemperature of 70° C. may be equal to 2190 (2370−56−60−64). As anotherexample, the target Dtemp corresponding to the target operatingtemperature of 1° C. may be equal to 2454 (2370+24+60). Target Dtempvalues corresponding to each of the values listed in column 350 may becomputed in this way. The values of FIG. 7 are merely illustrative. Ingeneral, the temperature coefficient of sensor 100 may be any positiveor negative constant, and target Dtemp values may be computed using thisapproach for any number (or range) of desired target operatingtemperatures.

Once the target Dtemp values have been computed, test system 110 may beused to measure the TX output power levels for DUT 10 at each of thetarget operating temperatures. At step 400 of FIG. 8, test host maydirect temperature control unit 120 to set the temperature withinchamber 118 to a selected target temperature other than the referencetemperature (e.g., the oven temperature may be set to 39° C.).

At step 402, sensor 100 may be used to measure Dtemp n times. Themeasured Dtemp values may be fed to test host 112. Test host 112 maycompute an average Dtemp based on the measured Dtemp values. Test host112 may determine whether the average Dtemp value is sufficiently closethe target Dtemp corresponding to the target temperature currentlyselected for calibration. If the magnitude of the difference between theaverage Dtemp and the target Dtemp exceeds a predetermined threshold,test host 112 may adjust temperature control unit 120 accordingly untilthe difference between the average Dtemp and the target Dtemp is lessthan the predetermined threshold.

At step 404, Dtemp measurements may be read back from DUT 10, andwireless communications circuitry 12 may be turned on (e.g., transceivercircuitry 14 and power amplifier circuitry 20 may be placed in an activetransmission state). At step 406, test host 112 may configure DUT 10 sothat power amplifier circuitry 20 is set to operate in the low gainmode.

At step 408, tester 114 may be used to measure the output power level ofpower amplifier circuitry 20 while sweeping the radio-frequency gainindex from RGI_(MIN) to RGI_(MAX) (e.g., from 0 to 31). In particular,transceiver 14 may be configured to output radio-frequency test signalsusing desired modulation schemes (at different data rates) at desiredfrequencies (in different frequency bands and channels). If desired, DUT10 may again record Dtemp to ensure that the internal temperature of DUT10 has not changed by an unacceptable amount since step 402 (e.g., mDtemp measurements may be stored in circuitry 102 after the output powerlevels have been measured using tester 114).

At step 410, test host 112 may configure DUT 10 so that power amplifiercircuitry 20 is set to operate in the high gain mode, and tester 114 maybe used to measure the output power level of power amplifier circuitry20 while gain index is swept from RGI_(MIN) to RBI_(MAX) (e.g., theoperations of step 408 may be repeated for characterizing the outputefficiency of circuitry 20 in high gain mode). If desired, DUT 10 mayagain record Dtemp to ensure that the internal temperature of DUT 10 hasnot changed by an unacceptable amount since step 408.

At step 412, wireless communications circuitry 12 may be turned off(e.g., transceiver circuitry 14 and power amplifier circuitry 20 may beplaced in the idle mode). Processing may loop back to step 400 if thereare additional target temperatures levels for which DUT 10 should becalibrated, as indicated by path 414.

FIG. 9 shows a table of illustrative transmit power measurementsgathered during step 408 of FIG. 8. These values may be measured at thesame transmit settings as those described in connection with FIG. 6except at a new target operating temperature. Notice that to achieve atarget temperature of 39° C., the oven temperature may only be set to35.4° C. so that Dtemp1 and Dtemp2 are sufficiently close to the targetDtemp of 2314 (see, FIG. 7). In general, the TX power levels measured athigher temperatures (e.g., temperatures greater than 25° C.) tend to belower than the baseline TX power levels measured at 25° C., whereas theTX power levels measured at lower temperatures (e.g., temperatures lessthan 25° C.) tend to be higher than the baseline power levels measuredat 25° C. Test data may be gathered in this way for each of the targetoperating temperatures using test system 110.

When test data has been gathered for each of the target operatingtemperatures, the illustrative steps of FIG. 10 can be performed. Atstep 500 of FIG. 10, test host 112 may be used to compute poweramplifier output power offset compensation values for each of the targetoperating temperatures. The output power offset compensation values may,for example, be calculated by subtracting the measured TX power levelassociated with each target temperature from the baseline TX power level(i.e., the measured TX power level associated with the referencetemperature). As shown in FIG. 11A, an offset ΔP1 may be computed forthe target operating temperature of 54° C., whereas an offset ΔP2 may becomputed for the target operating temperature of −15° C. (e.g., theamount of offset at each target temperature can be obtained by computingthe difference between the measured TX power at each of the targettemperatures and the measured TX power at the reference temperature).

At step 502, the computed offset compensation values may be stored inDUT 10 (e.g., the offset compensation values may be burned intonon-volatile memory that is part of storage and processing circuitry16). At step 504, DUT 10 may be configured in signaling mode (e.g., DUT10 may communicate with a radio communication tester by establishing aprotocol-compliant communications link with the radio communicationtester) to ensure that DUT 10 is transmitting signals at satisfactoryoutput power levels during normal user operation.

Once DUT is loaded with the offset compensation values, DUT 10 maycontrol power amplifier circuitry 20 based on these compensation valueswhile continuously monitoring its operating temperature usingtemperature sensor 100. As an example, consider a scenario in whichsensor 100 in DUT 10 generates Dtemp indicating that the currentoperating temperature of DUT 10 is equal to 25° C. DUT 10 may retrieve acorresponding offset compensation value of zero from non-volatile memory16 and may configure power supply circuitry 38 to supply power amplifiercircuitry 20 with a nominal power supply voltage of 1.0 V (see, e.g.,FIG. 11B).

As another example, consider a scenario in which sensor 100 in DUT 10generates Dtemp indicating that the current operating temperature of DUT10 is equal to 54° C. DUT 10 may retrieve a corresponding offsetcompensation value of −2 (reflective of a power amplifier efficiencydegradation) from non-volatile memory 16 and may therefore configurepower supply circuitry 38 to supply power amplifier circuitry 20 with aproportionally elevated power supply voltage of 1.1 V.

As another example, consider a scenario in which sensor 100 in DUT 10generates Dtemp indicating that the current operating temperature of DUT10 is equal to 16° C. DUT 10 may retrieve a corresponding offsetcompensation value of 1 (reflective of a power amplifier efficiencyimprovement) from non-volatile memory 16 and may therefore configurepower supply circuitry 38 to supply power amplifier circuitry 20 with aproportionally reduced power supply voltage of 0.96 V. Generally, offsetcompensation values corresponding to temperature levels other than thetarget operating temperatures may be interpolated or extrapolated basedon the measured data.

The example described in connection with FIG. 11B in which the gain ofpower amplifier circuitry 20 is adjusted by varying Vcc based on thecalibrated offset compensation values is merely illustrative and doesnot serve to limit the scope of the present invention. If desired, theoffset compensation values obtained during calibration operations may beused to adjust the gain of power amplifier circuitry 20 in any suitablefashion by providing appropriate control signals via path 44.

The foregoing is merely illustrative of the principles of this inventionand various modifications can be made by those skilled in the artwithout departing from the scope and spirit of the invention. Theforegoing embodiments may be implemented individually or in anycombination.

What is claimed is:
 1. A method of using a test system to calibrate anelectronic device, wherein the test system includes a radiocommunication tester and a test chamber in which the electronic deviceis placed during calibration, the method comprising: while the testchamber is set to provide a first a first internal chamber temperature,obtaining baseline measurement data from the electronic device with theradio communication tester; while the test chamber is set to provide asecond internal chamber temperature that is different than the firstinternal chamber temperature, obtaining additional measurement data fromthe electronic device with the radio communication tester, wherein theelectronic device includes wireless communications circuitry configuredto generate radio-frequency test signals during calibration, and whereinobtaining the baseline measurement data and the additional measurementdata comprises obtaining radio-frequency output power measurementsassociated with the radio-frequency test signals using the radiocommunication tester; and computing calibration data for the electronicdevice by comparing the additional measurement data to the baselinemeasurement data.
 2. The method defined in claim 1, wherein comparingthe additional measurement data to the baseline measurement datacomprises computing differences between the additional measurement dataand the baseline measurement data.
 3. The method defined in claim 1,further comprising: storing the calibration data in the electronicdevice, wherein the electronic device is configured to operate in normaluser operation using settings based on the stored calibration data. 4.The method defined in claim 1, wherein the electronic device includespower amplifier circuitry, and wherein the test system further includesa test host, the method further comprising: with the test host,configuring the power amplifier circuitry in the electronic device tooutput radio-frequency test signals using a plurality of radio-frequencygain settings at desired frequencies.
 5. The method defined in claim 1,wherein the test system further includes a power supply unit, the methodfurther comprising: with the power supply unit, proving power to theelectronic device during calibration; and with the power supply unit,monitoring power consumption levels for the electronic device duringcalibration.
 6. The method defined in claim 1, wherein the secondinternal chamber temperature comprises a target temperature level in alist of predetermined target temperatures levels to be calibrated, themethod further comprising: calibrating the electronic device whilesetting the test chamber to each target temperature level in the list ofpredetermined target temperature levels; and computing calibration datafor each target temperature level in the list of predetermined targettemperature levels.
 7. The method defined in claim 1, wherein theelectronic device includes power amplifier circuitry, wherein computingthe calibration data for the electronic device comprises computingoutput power offset compensation values for the power amplifiercircuitry, and wherein the output power offset compensation valuesconfigure the power amplifier circuitry to output radio-frequencysignals at satisfactory levels across different device operatingtemperatures.
 8. The method defined in claim 1, wherein the electronicdevice includes power amplifier circuitry, antenna structures, and atransmission line path interposed between the power amplifier circuitryand the antenna structures, and the method further comprising: couplingthe radio communication tester to the transmission line path using aradio-frequency test probe, wherein the antenna structures areelectrically decoupled from the power amplifier circuitry when theradio-frequency test probe is coupled to the transmission line path. 9.A method of using a test system to calibrate an electronic device havinga temperature sensing circuit operable to provide a sensor output value,wherein the test system includes a test chamber in which the electronicdevice is placed during calibration, the method comprising: while thetest chamber is set to provide a first internal chamber temperature,obtaining a baseline sensor output value using the temperature sensingcircuit in the electronic device; and computing target sensor outputvalues for each target calibration temperature level in a predeterminedlist of target calibration temperature levels based on the baselinesensor output value and a temperature coefficient associated with thetemperature sensing circuit, wherein each of the computed target sensoroutput values specifies a respective value for which the sensor outputvalue generated by the temperature sensing circuit has to match at acorresponding target calibration temperature level in the predeterminedlist of target calibration temperature levels.
 10. The method defined inclaim 9, wherein the temperature sensing circuit comprises a thermistor,and wherein the temperature coefficient associated with the thermistoris a fixed value.
 11. The method defined in claim 9, further comprising:configuring the test chamber to provide a second internal chambertemperature that is different than the first internal temperature; andwhile the test chamber is configured to provide the second internalchamber temperature, obtaining a measured sensor output value using thetemperature sensing circuit.
 12. The method defined in claim 11, whereinthe test system further includes a radio communication tester, themethod further comprising: determining whether the measured sensoroutput value is sufficiently close to a corresponding one of the targetcalibration sensor output values; in response to determining that themeasured sensor output value is sufficiently close to the correspondingtarget calibration sensor output value, using the radio communicationtester to obtain desired radio-frequency measurements from theelectronic device; and in response to determining that the measuredsensor output value is not sufficiently close to the correspondingtarget calibration sensor output value, reconfiguring the test chamberto provide a third internal chamber temperature that is different thanthe second internal chamber temperature.
 13. The method defined in claim10, wherein the test system further includes a radio communicationtester, the method further comprising: while the test chamber is set toprovide the first internal chamber temperature, using the radiocommunication tester to obtain baseline radio-frequency measurementsfrom the electronic device; and while the test chamber is configuredsuch that the sensor output value is sufficiently close to one of thetarget sensor output values, using the radio communication tester toobtain additional radio-frequency measurements from the electronicdevice.
 14. The method defined in claim 13, wherein the electronicdevice further includes wireless communications circuitry, the methodfurther comprising: computing calibration data for the wirelesscommunications circuitry by comparing the additional radio-frequencymeasurements to the baseline radio-frequency measurements.
 15. A methodof operating an electronic device that includes wireless communicationscircuitry and a temperature sensing circuit, the method comprising:storing calibration settings on the electronic device; with thetemperature sensing circuit, monitoring an operating temperature for theelectronic device; in response to detecting a first operatingtemperature, configuring the wireless communications circuitry in afirst gain mode by supplying at least a portion of the wirelesscommunications circuitry with a first power supply voltage according tothe stored calibration settings; and in response to detecting a secondoperating temperature that is greater than the first operatingtemperature, configuring the wireless communications circuitry in asecond gain mode by supplying the portion of the wireless communicationscircuitry with a second power supply voltage that is greater than thefirst power supply voltage according to the stored calibration settings.16. The method defined in claim 15, wherein the temperature sensingcircuit comprises a thermistor having a constant temperaturecoefficient.
 17. The method defined in claim 15, wherein the wirelesscommunications circuitry includes power amplifier circuitry having agiven number of amplifier gain stages, and wherein configuring thewireless communications circuitry using the selected gain settingcomprises selectively activating at least some of the amplifier gainstages.
 18. The method defined in claim 17, wherein the electronicdevice further includes adjustable power supply circuitry, and whereinconfiguring the wireless communications circuitry using the selectedgain setting further comprises providing an adjustable power supplyvoltage to the power amplifier circuitry with the adjustable powersupply circuitry.
 19. The method defined in claim 15, wherein thewireless communications circuitry includes power amplifier circuitry,wherein storing the calibration settings comprises storing poweramplifier output power offset compensation values corresponding todifferent device operating temperatures, and wherein configuring thewireless communications circuitry using the selected gain settingcomprises adjusting the power amplifier circuitry based on acorresponding power amplifier output power offset compensation value toensure that the power amplifier circuitry is outputting radio-frequencysignals at satisfactory signal levels.